What formula does this calculator use?

Hydrostatic test pressure uses the API 5CT §10.12.3 formula: p = (2 × f × YS_min × t) / D, where f = 0.6 for H40/J55/K55 with OD > 244.5 mm, f = 0.8 for all other grades. Pipe weight uses W = 0.02466 × t × (OD − t).

Which API 5CT grades are supported?

H40, J55, K55, N80-1, N80Q, L80-1, L80-13Cr, C90, T95, C110, P110, and Q125, with minimum yield strength values pre-loaded from API 5CT.

What units does the calculator accept?

OD and wall thickness in millimetres (mm). Pressure results are displayed in MPa, bar, and psi; pipe weight in kg/m and lb/ft.

Are results suitable for final casing design?

No. Results are reference values for planning and feasibility only. Final casing design requires full API TR 5C3 analysis including biaxial loads, wear allowances, and appropriate design safety factors.

API 5CT Pressure & Weight Calculator

This calculator applies the API 5CT / TR 5C3 formulas for two key OCTG properties: plain-end weight per metre (W = 0.02466 × t × (OD − t)) and hydrostatic test pressure per API 5CT §10.12.3 (p = 2 × f × YS_min × t / D). Grades H40 through Q125 per API 5CT are pre-loaded with minimum yield strength values; enter OD and wall thickness in mm.

API 5CT / TR 5C3 — OCTG casing and tubing. Results are reference values only — verify against full casing design before use.

Pipe Weight per Metre

W = 0.02466 × t × (OD − t) | API 5C3

OD (mm) Wall thickness (mm)

Hydrostatic Test Pressure (API 5CT §10.12.3)

p = (2 × f × YS_min × t) / D | Rounded to nearest 0.5 MPa. Max 69.0 MPa.

f = 0.6 for H40, J55, K55 with OD > 244.5 mm (9⅝"); f = 0.8 for all other grades and sizes.

OD (mm) Wall thickness (mm) Grade

Quick Unit Converter

Results update as you type.

Inches → mm

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ksi → MPa

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lb/ft → kg/m

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bar → psi

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Engineering Disclaimer: Results are reference values only. Full casing design must account for biaxial loading, safety factors, wear, corrosion allowance, and other well-specific parameters per API TR 5C3 and applicable well design standards. Always verify with qualified casing design software before use.

How to Use This Calculator

Enter OD and nominal wall thickness in millimetres and select the API 5CT grade. The weight calculator returns plain-end (PE) weight; nominal weight as tabulated in API 5CT is slightly higher due to coupling make-up. The test pressure calculator applies the §10.12.3 formula with grade-dependent f coefficient and the 69 MPa cap.

Underlying Formula and Standard

API 5CT §10.12.3 and API TR 5C3 are the governing documents for OCTG hydrostatic test pressure and mechanical property calculations.

Plain-end weight (kg/m): W = 0.02466 × t × (OD − t), where OD and t are in mm. Divide by 1.4882 to convert to lb/ft.

Hydrostatic test pressure (API 5CT §10.12.3): p = (2 × f × YS_min × t) / D. f = 0.6 for H40, J55, K55 with OD > 244.5 mm; f = 0.8 for all other grades and sizes. Maximum 69.0 MPa. Rounded to nearest 0.5 MPa.

Worked Example — 9-5/8" 47 lb/ft L80 Casing

Inputs: OD = 244.5 mm, wall thickness = 11.99 mm, L80 (f = 0.8).

Plain-end weight: W = 0.02466 × 11.99 × (244.5 − 11.99) = 68.7 kg/m (46.2 lb/ft). Nominal weight including coupling = 47 lb/ft per API 5CT.
Test pressure (§10.12.3): p = (2 × 0.8 × 552 × 11.99) / 244.5 = 43.3 MPa → rounded to nearest 0.5 MPa = 43.5 MPa. Below the 69 MPa cap.

Typical Internal Yield Pressure Values

Internal yield pressure per API 5C3 (P = 0.875 × 2 × YS_min × t / D, using the 0.875 minimum wall factor). Not the same as the §10.12.3 mill test pressure computed by the calculator above. Reference values only — verify against API 5CT tables for final design.

Size	WT (mm)	Grade	~Weight	Int. Yield Pressure
5-1/2" (139.7 mm)	9.17	L80	20 lb/ft	63.5 MPa / 635 bar
7" (177.8 mm)	9.19	L80	26 lb/ft	49.9 MPa / 499 bar
9-5/8" (244.5 mm)	11.99	L80	47 lb/ft	47.4 MPa / 474 bar
9-5/8" (244.5 mm)	11.99	P110	47 lb/ft	65.1 MPa / 651 bar
13-3/8" (339.7 mm)	8.69	J55	~48 lb/ft	17.0 MPa / 170 bar

When to Use This Calculator vs Full Casing Design

This calculator is appropriate for initial sizing checks, cross-referencing vendor data against API 5CT tables, and bid evaluation. It should not replace full casing design per API TR 5C3 and ISO 10400. Complete design must account for biaxial loading (combined tension and pressure loads in deviated wells), wear allowance in rotating sections, temperature derating of yield strength at depth, mud weight and pore pressure at total depth, and connection body and thread strength. Use qualified casing design software and have results reviewed by a well engineering team before procurement.

What is the API 5CT hydrostatic test pressure formula?

API 5CT §10.12.3 defines the mill hydrostatic test pressure as p = (2 × f × YS_min × t) / D, rounded to the nearest 0.5 MPa and capped at 69.0 MPa (10,000 psi). The coefficient f = 0.8 for most grades and sizes; f = 0.6 for H40, J55, and K55 grades with OD greater than 244.5 mm (9⅝"). YS_min is the specified minimum yield strength of the grade.

Why is there a 69 MPa maximum on the test pressure?

API 5CT §10.12.3 caps the standard hydrostatic test pressure at 69.0 MPa (10,000 psi) for all grades. For C110, P110, and Q125 grades where the formula would compute a higher value, the standard test pressure is limited to 69.0 MPa; the optional test pressure uses the calculated value directly. This limit is set by practical mill test equipment capacity.

What is the difference between mill test pressure and design pressure?

The mill hydrostatic test pressure confirms pipe body integrity — it is not a design pressure and has no direct relationship to operating pressure. Field operating pressure should be set with appropriate safety factors per the applicable well design code (API TR 5C3, ISO 10400). The test pressure is used as a quality acceptance criterion during manufacturing, not as a design rating.